/Engine/Source/Runtime/InteractiveToolsFramework/Public/BaseGizmos/GizmoMath.h
Find the closest pair of points on a 3D line and 3D ray. Returns the points and line-equation parameters on both the line and ray.
namespace GizmoMath { void GizmoMath::NearestPointOnLineToRay ( const FVector & LineOrigin, const FVector & LineDirection, const FVector & RayOrigin, const FVector & RayDirection, FVector & NearestLinePointOut, float & LineParameterOut, FVector & NearestRayPointOut, float & RayParameterOut ) }